Pressure regulating apparatus for a hydraulic control system



L. SADLER ET AL PRESSURE REGULATING APPARATUS FOR A HYDRAULIC CONTROLSYSTEM Original Filed Dec. 4, 1951 A ril 29, 1958 2 Sheets-Sheet 1 NMNNNN NNw SEN ANN SQ SN h wmw ' INVENTORS. Card/J fiazievzlioerifiiiaeggrem Geazyaf/f/emanaom,

April 29, 1958 c. L. SADLER ET AL 2,332,197

PRESSURE REGULATING APPARATUS FOR A HYDRAULIC CONTROL SYSTEM OriginalFiled Dec. 4, 1951 2 Sheets-Sheet 2 1% 53 3 1&4

PRESSURE REGULATHQG APPARATUS Willi. A HYDRAULHI OUNTRUL SYSTEM Carl L.Sadler, Roclri'ord, llh, Robert 'Eisengrein, Skaneateles, N. 35., andGeorge H. Herntansen, San Diego, Calif., assigncrs to Sundstrand Co., acorporation oi Illinois Original application lfvecernber d, 1951, SerialNo. 259,872, new Patent No. Ldifidlil, dated August Ill, 1957. Dividedand this application September 2, W55, Serial No. 532,213

2 Claims. (Cl. fill-52) This invention relates to control means and moreparticularly to hydraulically operated control means.

This application is a division of our co-pending application Serial No.filed December 4, 1951, now Patent Number lllilil l2.

It is a general object of this invention to provide a new and improvedcontrol means.

While it will be clear to those skilled in the art that the presentinvention is usable in many hydraulic sys terns, it is particularlyadapted for use, and is shown incorporated in, a hydraulic controlsystem for a hydrauits transmission which is interposed between adriving element and a driven element and provided with adjust-- ablemeans for varying the output of the transmission to maintain the speedof the driven element constant regardless of variations in the speed ofthe driving element, with the control being provided with ahydraulically operated device for adjusting the adjustable means andincluding a governor driven the driven element and adapted to operatevalve means to supply of fluid to the device.

Thus a more specific object of the invention is to provide, in ahydraulic circuit for a control of the type de scribed in the precedingparagraph, a pressure differential valve interposed between a source ofhydraulic fluid under pressure and the valve means and in which thecircuit is doubled back through the ditlerential pressure valve with thevalve serving to produce a substantially constant pressure diilerentialacross the valve means regardless of changes in the pressure fromsource.

Yet another object of the invention is to produce a differentialpressure valve adaptable for use in control systems of the typedescribed above which includes a casing having a bore, a spool valveslidable in the bore having two spaced lands, the valve being soconstructed as to be connected to a source of hydraulic fluid and to thevalve means through the intermediate portion of t. e bore with one endof the bore being subjected to fluid pressure from the source and withthe other end of the bore being subjectet to fluid pressure from thevalve means.

Other and further objects of the invention will be readily apparent fromthe following description and accompanying drawings, in which:

Fig. l is a schematic diagram showing the control means of thisinvention as used with a hydraulic transmission interposed between adriven shaft and a driving shaft for driving the transmission;

2 is a schematic diagram of the electrical circuit for the overspeed andtz nderspeed switches;

Fig. is an enlarged sectional view of the governor control and associLed driven mechanism; and

4 is an enlarged. sectional view the differential pressure regulatingvalve.

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and ii,d32,l'i .ented. Apr. 29,.1953 will. herein be described in detail one specific embodiment, withthe understanding that the present disclosure is to be considered as anexemplification of the principles ot' the invention and is not intendedto limit the invention to the embodiment illustrated. The scope of theinvention will be pointed out in the appended claims.

the exemplary disclosure made in the drawings the invention is shown asembodied in a transmission designed for employment in driving a teviceat a constant speed from power source, which may vary widely in speed.it is contemplated that the device of this invention will be most widelyused for driving alternators in an aircraft and thus is provided with aninput or driving element M adapted for connection to the aircraftengine. The transmission is provided with an output or driven element 11adapted to be connected to a device to be driven, for example analternator 12. A hydraulic power and speed conversion unit is providedto connect the driving element ill with the driven element ill. Means idis provided for varying the operation of the transmission to obtain aconstant speed of the driven element ll though the driving element illvaries either above or below the desired speed of the driven element.Thus, in the exemplary embodiment shown, the device to be driven isalternator, such as a 400-cycle alternator adapted to be driven at aconstant speed of 6,000 R. P. M. while the driving element varies inspeed from 2,190 to 8,006 R. l M. or more. (Iontrol means is providedconstantly and automatically to govern the means i l to produce aconstant speed of the driven element ll regardless of the speed at whichthe driving element lid is driven by the power source.

As best seen in Fig. l, the tra smission includes the hydraulic powerand speed conversion unit 13. This unit in turn is comprised of a pump Pand a motor M, each of the reciprocate-1y piston type, with the pumphaving a Wobbler l5 adjustable in varying amounts to either side ofneutral position to vary the direction as well as the quantity of fluiddischarged from the pump to the motor. The hydraulic conversion unit ashere shown is of the rotatable barrel or cylinder block type, and hasthe pump as well as the motor cylinders formed in the same rotatablecylinder block 16. Such a construction permits of readily obtainingrotation of the motor shaft at a speed either above or below that of thecylinder block, and hence of obtaining the constant speed or" the motorshaft regardless of the rate of rotation of the cylinder block byadjustment of the Wobbler Adjustment of the webbler 15 with respect toneutral determines whether the motor shaft is driven faster or slowerthan the cylinder block 16 and the extent that the Wobbler 15 is swungfrom its neutral position determines the differential between the speedsof the cylinder block and the motor shaft, the pump and motor partsbeing locked and the cylinder block and the motor shaft rotating at thesame speed when the Wobbler is in neutral position.

The rotatable cylinder block 16 comprises a pump block 17, a motor block18 and an annular spacer plate 19. The pump and motor blocks areassembled in line so as to maintain the outside diameter of the cylinderblock id to a minimum, adapting the unit for high speed operation inwhich centrifugal forces are kept at a minimum. The pump and motorblocks are secured in end to end relationship, being spaced only by theplate 19. To that end, the blocks 17 and iii are formed respectivelywith radially outwardly extending flanges 2d and 21 and passing throughthese flanges and through the plate 19 are a plurality of bolts 22 bymeans of which the parts are secured together in fluid-tightrelationship.

The cylinder block 16 is rotatably supported in two sets of bearings 23and 24. i

The face of the pump block 17 adjacent the plate 19 is formed with ashallow circular recess which with the plate 19 forms a valve chamber atall times in free communication with a chamber 26 formed by the centerof the annular plate 19. Also formed in the block 17 is a plurality ofannularly arranged cylinders 27 disposed in parallel relationship withthe %is of the unit and opening at the righthand end as seen in Fig. 1through the end of the block 17 and opening at the left-hand end to thevalve chamber 25. The number of cylinders 27 is large, being in theorder of eighteen. Reciprocable in each cylinder 27 is a piston 28 andoperable to project in all positions from the right-hand end of thecylinder and in contact with the face of the wobbler 15.

Formed in the corresponding face of the motor block 18 is a shallow,circular recess 30 similar to the recess 25 and likewise forming withthe plate 19 a valve chamber in constant communication with the chamber26. The valve chambers 25 and 36 in addition to being in commu icationthrough the chamber 26 are in communication at their peripheries througha plurality of longitudinal passages 31 formed in the plate 19. Alsoformed in the motor block 18 is a plurality of annularly arrangedcylinders 32 disposed parallel with the axis of the transmission unitand opening at one end through the left-hand end of the block 18 and atthe other end opening to the valve chamber 30. Reciprocable in eachcylinder 32 is a piston 33 which is operable in all positions to projectfrom the lefthand end of the block 18. The motor cylinders, in theembodiment illustrated, correspond in number to the pump cylinders.

Operable in the valve chambers 25 and 30 are identical valves 35 and 36of the wheel type. Each valve is composed of a rim 37 of radial widthequal to the diameter of the cylinders, which rim has a close,fluid-tight but sliding fit between the end walls of the valve chamberin which it is located. The rim 37 is connected to and carried by thehub 38 through the medium of spokes which are spaced suificiently apartso as to leave a plurality of openings through the valve and which alsoare of reduced thickness compared to the rim 37 in order to permit aready flow of fluid from one side of the valve to the other as well ascircumferentially.

The valves 35 and 36 have a gyratory, as distinguished from a rotary,movement within the valve chamber, serv ing by such gyratory movement toconnect the cylinders in rotational sequence alternately to theperiphery of the respective valve chambers outwardly of the rim 37 andto the chambers inwardly of the rim 37, the cylinders being completelyclosed at the time of reversal of the direction of movement of thecorresponding piston. To impart such gyratory movement to the valverelative to the valve chambers the valves are given an eccentricmounting. Thus the eccentric upon which the valve 35 is mounted isstationary and comprises an elongated member 39 secured at 40 to aclosure for the transmission unit.

Completing the motor is a swash plate comprising an outer annular member51 positioned for constant engagement with the left-hand projecting endsof the motor pistons 33. The annular member 51 is, through the medium ofthrust ball bearings 52, rotatably mounted on a shaft forming member 53.Suitable and complementary raceways, disposed at a fixed inclination tothe axis of the shafbforming member 53, are formed in the outer annularmember 51 for the bearings. The shaft-forming member 53 terminates in aneccentric 54 upon which the valve 36 is rotatably mounted.

It is believed apparent from the foregoing that the cylinder block 17constitutes the driving part and the member 53 constitutes the drivenpart of the hydraulic unit.

For rotating the cylinder block there is secured to the drive shaft 10 aspur gear having teeth meshing with the teeth of a second spur gear 61fixed to the cylinder block 16. The shaft-forming member 53 carriesthereon a gear 62 which meshes with a second gear 63 fixed to a 4 driveshaft 64 for driving the alternator 12. Fixed upon the shaft 11 is aworm gear 70 which meshes with a worm 71 which through a right anglebevel gear system generally indicated '72 serves to rotate thefiyweights of a centrifugal governor 74 which forms a part of thecontrol system of this invention.

Also fixed to the shaft 11 is another spur gear '75 which meshes with agear 76 connected to a makeup oil pump 77 and a scavenge oil pump 78 todrive the same. The makeup oil pump 77 receives its oil through aconduit 80 connected to a reservoir (not shown) of oil and dischargesinto another conduit 31 which passes the oil through a filter 82 andthrough a first passageway 33 formed in the member 39. The passageway 83opens to the chamber 26 to supply makeup oil to the pump and motor unit.The volume of oil supplied to the chamber 26 is in excess of the makeupoil requirements so that the oil serves not only makeup purposes butalso serves to cool tr e transmission. The excess oil from the chamber26 is returned through the member 3? by means of a second passageway 84formed therein. The passageway 34 connects with a conduit 85 whichterminates in a pressure relief val 'e 86 designed to maintain themakeup oil at a pressure of about 300 p. s. i., oil over that pressureis discharged by the valve 86 through an opening 87 into a segregatedspace 88 formed in the casing housing the pump and motor.

For lubricating the pump and motor the space 88 is defined in part by awall 89 which is provided with a number of lubricating oil jetsindicated at 94 for spraying oil on the various moving parts of thetransmission with the pressure within the space 38 being maintained atabout 20 p. s. i. by the pressure relief valve 91. Discharge from thepressure relief valve 91 through the opening 92 is directed into thesump of the casing from which it is scavenged by the scavenging pump 78.

The control device 14 is provided for controlling the angle of thewobbler 15 and to this end comprises a pair of opposed piston andcylinder devices. Thus there provided a cylinder in which a piston 101is reciprocable, the piston being opposed by a second piston 102reciprocable in a second cylinder 103. The pistons are connectedtogether by the sleeve 104 and are each con-- nected by means of therods 105 and 106 to an arm 107 fixed to the wobbler 15. Thus as thepistons reciprocate in their respective cylinders the wobbler is tiltedfrom the angle shown toward the vertical position and beyond to alterthe operation of the hydraulic transmission 13.

As previously pointed out, the purpose of the control device is tomaintain the speed of the driven shaft 11 and hence of the alternator 12at a constant predetermined value regardless of changes in speed in thedrive shaft 10. Changes in relative speeds between the shafts 10 and 11are eifected by changes in position of the wobbler 15 and the controldevice 14 which serves to adjust the position of the wobbler. To effectthe control of the driven member there is provided the centrifugalgovernor 74 which is operatively connected into the hydraulic circuitprovided for moving the pistons 100 and 102 so as to vary the positionof the wobbler as the speed of the driven shaft 11 departs from apredetermined value.

To this end the cylinder 103 is connected by means of the conduit 110 tothe space 88 and thus there is constantly applied to the piston 102 thelubricating oil pressure of approximately 20 p. s. i. In the absence ofpres sure in the cylinder 100 this pressure would serve to move thepiston 102 to its extreme rightward position, thus tilting the wobblerfrom the position shown through neutral to its opposite extremeposition. To deliver pressure to the cylinder 100 which, because thepistons are of equal area, must be in excess of lubricating oilpressure, the makeup oil pressure in the conduit 85, which as previouslynoted is maintained at 300 p. s. i., is piloted ofi through a conduit111 and through a pressure difierential valve generally indicated at 112through a gover- 191 valve. 113. controlled by the governorand thence.into a.c onduit 114; which. is ultimately connected to the cylinder;100. Thus, there is available for application to the P Ston.101-hydraulic fluid. under a pressure of as high as 300p. s. i.

The differential pressure valve 112 (see Fig. 5) comprises a casing 115.having a bore 116 therein in which thereis slidably received a spooltype valve 117 having a first land 118 and a second land 119. Theconduit 111 is connected to the bore 116 through an internal passageconnected to a port 120 intermediate the two lands. outport 121 is.provided in the bore to which there iS connected another conduit 122which leads'to the governorvalve member 113. Also connected to theoutport is a fluid passage 123 formed in the casing which connects thatport with one end 124 of the bore. Movement of the spool valve 117within the bore controls the outport 121 so as to regulate the amountand pressure of fluid delivered into the conduit 122.

The conduit 114 leading from the governor valve 113 connects into asolenoid dump valve 130 and thence into a conduit 131. The conduit 131connects into a sleeve 132 orpethe pressure difierential valve 112, thesleeve being coiicentric with the other end 133 of the bore, with theconnection being. through an internal passage connected to a port 133.Located in the sleeve 132 is a spring 134 which bears against a closure135. closing the outer. end of thesleeve and against a thrust washer 136adapted to contact the spool valve 117 constantly to urge the spoolvalve to the right-hand end 124 of the bore. Also located in the end 132of the bore is another port 137 -tQWh Ch is. connected a conduit 138which opens into thecylinder 100.

;,1?IOH1;1118 foregoing it will be noted that the end 124 of the bore,that is on the right side of the land 118, is subiegted to the pressureas regulated by. the land 118 which passes into the outport 121. Thispressure serves to force the spool valve 117 to the left. This force isresisted by.the spring 134 and also by the pressure in the sleeve 132 asdelivered thereto by the governing valve 113. Thus should there be anincrease in makeup pressure in the conduit 111 this pressure istransmitted to the end 124 through the passage 123 and serves to movethe spool valve to the left bringing the land 118 at least partiallyacross the port 121 to reduce the pressure delivered into the conduit122. Similarly should there be a slight drop in makeup oil pressurethere is a consequent drop of pressure in the end 124 permitting thespring and the fluid pressure in the sleeve 132 to shift the spool valveto the right uncovering more of the port 121 to increase the pressuredelivered to the governor valve 112. Because of the pressuredifferential valve, slight variations in oil pressure are immediatelycompensated for without waiting for a speed change, which wouldotherwise result, to effect compensation. Thus the pressure differentialacross the governor control valve 113 remains substantially constant sothat for any given operating position of that valve, a regulatedquantity of oil will flow to the wobbler control cylinder 100.Furthermore, should there be a sudden load imposed on the transmissionwhich would tend to cause the wobbler to tilt toward an underdriveposition the pressure in the cylinder 100 and hence in the sleeve 132would be increased, shifting the spool valve 117 to the right uncoveringmore of the port 121 and thus increasing the pressure delivered to thecylinder 103 to maintain the wobbler in proper position.

The governor 74 (see Fig. 4) includes a casing 140 in which there ismounted an annular bushing 141 which rotatably supports a sleeve 142which carries at its upper end a pair of flyweights 143 pivotallymounted thereon and each flyweight is provided with an arm 144 connectedto the stern 145 of the governor control valve 113. Rotation of thesleeve 142 is achieved through a drive shaft 146 rotated by the rightangle drive mechanism 72. The

valve. 113 isv provided. with a. reduced portionterminatingin a land148v which makes substantial. fluid-tight contact with an elongatedpassage 149 extending through the center of the sleeve and in which thestem 145 is recipro-. cable. A main spring 150 is located within achamber portion 151 adjacent the upper end of the casing and has one endbearing against an adjustable nut 152 threaded in the top of the casingand the other end bears against a thrust washer 153. The washer 153seats on a bearing 154 which is positioned to be contacted by the arms144 as they pivot upwardly in response to the rotation of the flyweights143. Located the main spring 150 and operating in parallel therewith isa control spring 155 whose lower end bears against the thrust washer 153and whose upper end is secured to a rod 156 which extends through acentral opening in the nut 152 and bears against an eccentric cam 157secured through a gear reduction drive 158 to a motor 207. Anapproximate control of the speed of the driven shaft is maintainedthrough the main spring 150 and the control spring 155 is provided formaking fine adjustments as will hereinafter be described.

It is believed to be apparent from the foregoing that as the sleeve 142is rotated with rotation of the drive element 11 the flyweights 143 tendto move outwardly bythe centrifugal force imposed upon them, whichoutward movement is resisted by the main spring 150. Under normal andproper operating conditions the flyweights move out until theircentrifugal force is oifset by the pressure of the main spring and insuch movement lift the valve stem to bring the land 148 into. control ofa port 160 connected to the passage 149. Oil in the conduit 122 isadmitted to that passage through a port 161 and hence may flow into theconduit 114 and eventually into the cylinder 100 to offset the constantforce imposed on the piston 102 by the lubricating oil pressure and thevarying force imposed by wobbler return movement. In the event the speedof the driven element drops below the desired speed the sleeve 142 willrotate at a lower speed, hence the valve stem and land 148 will movedownwardly permitting more oil to flow through the port 160 and into thecylinder 100, while should the speed of the driven element 11 increasebeyond the desired amount the land 148 will be moved upwardly to aposition blocking the port 160 or be moved about it so that oil pressurein the cylinder 100 may be drained into the passage 149. From thispassage oil may pass into a space 162 surrounding the sleeve throughsmall openings 163 in the sleeve and thence into a drain 164 to thesump.

The right angle mechanism 72 (see Fig.4) includes a casing containingbevel gears and a centrifugal switch mechanism. Thus there is provided ashaft 171 which is secured to the worm 71 and to a bevel gear 172rotatably mounted on anti-friction bearings 173. The gear 172 mesheswith a second bevel gear 174 mounted in the bearings 175 and to whichthe shaft 146 is fixed for rotating the sleeve of the governor control.

The solenoid dump valve 130 (Figs. 1 and 2) includes a solenoidconnected to a stern 191 of a valve membar 192 reciprocable in a bore193 formed in the casing 194 of the dump valve. The solenoid is shown inits normal condition and if energized under conditions hereinafterdescribed the valve 192 is brought up into a position blockingcommunication between the conduits 114 and 131. The valve 192 isprovided with an internal port 195 which permits oil under pressure inthe end 132 to pass therethrough into the lower portion of the bore 193which in turn is connected by means of the conduit 195 to the sump torelieve pressure in the cylinder 100 and hence permit pressure in thecylinder 103 to shift the wobbler to its maximum underdrive position.

The controls described up to this point are sensitive to produce asubstantially constant speed of the driven element 11. To efiect thefine control necessary to produce The cam drive motor 207 is connectedthrough'the" reduction gear 158 to the cam 157 to rotate the same andhence to increase or decrease the tension of the control spring 150against the upper end of the valve stem 145, thus slight variations inthe control valve 113 are effected.

Centrifugally operated overspeed and underspeed switches are providedwithin the right angle drive 72. Switches are so designed as to preventthe alternator from being cut into the circuit until it has reached acertain predetermined minimum speed and also to move the speed controlmeans for the hydraulic transmission to maximum underspeed in the eventof malfunction of the control which imparts an excessive speed to thealternators.

To this end the bevel gear 172 is provided with a flange portion 250secured thereto on which are pivotally mounted a plurality of flyweights251. Each flyweight is provided with an arm 252 adapted, when pivoted bycentrifugal force operating on the flyweights, to move a rod 253 towarda switch assembly 254 located within the casing of the right angledrive; ,The rod 253 is held slidably within an opening 255 in apartition 256 within the housing by means of a groove 257 engaged by adetent mechanism 258. As the rod movesjto the left from .the positionshown in Fig. 4 it is moved into contact with a blade 260 of a knifeswitch, mechanism. The blade 260 is pivotally mounted at 263 and heldagainst the free end of the rod 253 by a plunger 261 urged thereagainstby a spring 262. Upon counterclockwise pivotal movement about the point263 the blade 260 is moved against the contact 264 of an underdriv'eswitch 265. Until the contact 264 is closed the alternator connected tothe hydraulic transmission involved is cut out of the electricalcircuit. When the alternator has reached the minimum operating speed thecontact 264 is closed to cut the alternator into the circuit by wellknown means. I

In the event the hydraulic transmission drives the alternator at anexcessive speed the flyweights 251 will force the rod 253 to the left toa greater extent until the knife arm 260 is brought against the contact266. This contact closes the circuit through the solenoid 190 to liftthe valve 192 therein to a position wherein the fluid in the conduit 131and hence the cylinder 100 will be dumped into the drain 196. This, ofcourse, effects an immediate reduction to the lowest possible speed ofthe driven element. To prevent the driven element from again beingspeeded up by th e operation of the governor,

the valve stem 192 is provided with a detent 270 at its lower end whichis engaged by a spring operated latch mechanism 271 to hold the stem inthe elevated position it obtains when the solenoid is energized. Thuswhen the solenoid is deenergized with decrease of speed, the valve 192remains in the dumping position until the latch and detent mechanism aremanually reset, which will presumably be after the condition whichcaused the overspeed has been corrected.

We claim:

1. In a hydraulic control circuit having a pump providing a continualsupply of fluid under pressure, a member to be subjected to saidpressure, and means providing a variable orifice intermediate the pumpand the member for governing the supply of fluid to said member, adifferential pressure regulating valve operatively interposed in saidcircuit comprising a casing having a bore, a spool valve slidable in thebore and having a pair of spaced lands, a port in the portion of thebore between the lands and connected to the pump, a second port in saidportion of the bore for supplying fluid under pressure to one side ofthe orifice of the governing means and controlled by one of the lands,means connecting one end of the bore to the pump, resilient means in theother end of thcg i'iore biasing the spool valve for movement toward thefirst mentioned end of the bore, and means connecting said other end ofthe bore into the circuit on the other side of the orifice andintermediate the governing means and the member.

2. A diflerential pressure regulating valve for regulating fluidpressure delivered from a pump providing a continual supply to agoverning means for said pressure with the governing means having a portcontrolled by a movable land to provide a variable orifice for flow offluid from said pump comprising a casing having a bore, a spool valveslidable in the bore and having a pair of spaced lands, a port in theportion of the bore between said lands adapted to be connected to saidpump, a second port in said portion of the bore and controlled by one ofsaid lands and adapted to be connected to said governing means on oneside of the orifice, a passage in the casing connecting said portion ofthe bore to one end of the bore to apply fluid pressure against thespool valve to urge the same toward movement toward the other end of thebore, resilient means in said other end of the bore and acting inopposition to said movement, and means for subjecting said other end ofthe bore to governed fluid pressure from the other side of the orificeof said governing means.

References Cited in the file of this patent UNITED STATES PATENTS2,167,328 Beggs July 25, 1939 FOREIGN PATENTS 948,925 France Feb. 7,1949

